[arch-projects] [archweb] [RFCv2] Add releng netboot to archweb

[Thomas Bächler]

This is the second WIP patch series to add the netboot environment
to archweb. I improved a few minor issues compared to the last
version.

- I have no idea if django properly caches this page, or if
  this requires extra configuration, as regenerating it every
  time seems like overkill.
- All files that iPXE needs to access must be served without
  SSL as far as I know.

To test it, set your archweb test environment to run on
 http://localhost:8000/
Download ipxe.lkrn from https://paste.xinu.at/OX7oU8/
and execute
 qemu-system-x86_64 -enable-kvm -kernel bin/ipxe.lkrn
or
 qemu-system-x86_64 -enable-kvm -kernel bin/ipxe.lkrn -cpu kvm32
(I hope this still works, cannot test right now)